The term “particulate material” refers to granular or powdered material such as sand, minerals, rock, gravel, grain, seed and other similar material.
Sorting or classifying devices are used in a number of industries, such as the construction, recycling and mining industries. These devices are used to separate particulate materials from other undesired substances based on the size of the particulate material. This type of classification is commonly done using screening techniques.
A known device for sorting particulate material takes the form of a rotary cylindrical screen having holes of a predetermined size with a series of rotating single row brushes located within the rotary screen. A screw auger feeds particulate material into the screen and the rotary brushes sweep the particulate material against the screens, causing particles below or at the predetermined size to fall through the holes in the screen and particles larger than the predetermined size to pass along the screen for rejection.
Sorting devices, including the known device, suffer from one or more of several disadvantages. In some devices, particles approaching the predetermined size can wedge into the holes of the screen. This disrupts the sorting process as well as requiring frequent maintenance of those devices. Many existing sorting devices require screen replacement in order to vary the size of sorting particulate material. Particles hitting the screen in some devices, often at high speed, can cause damage and wear to the screen.